In many applications of antenna arrays (or array antennas), whether communication systems, satellite communications (SatCom) systems, military radar systems, electronic intelligence (ELINT) systems, electronic counter measure (ECM) systems, electronic support measure (ESM) systems, aerospace systems, or biological or medical microwave imaging systems, there is a demand for large ultra-wideband (UWB), or even large ultra-ultra-wideband (U2WB), antenna arrays. UWB and (U2WB) antenna arrays operate at (or support) relatively large frequency bands. For example, U2WB antenna arrays can operate at frequency bands extending from 200 MHz to 60 GHz. In order for antenna arrays to support relatively high frequencies, the respective antenna elements (or radiating elements) are made smaller in size. In particular, the higher the maximum frequency supported by an antenna array, the smaller are the antenna elements of that array.
Also, increasing the size of an antenna array allows for accommodating a larger number of antenna elements and therefore improved antenna array performance. For example, increasing the size of an electronically-scanned array (ESA) antenna or an active ESA (AESA) antenna allows for accommodating a larger number of antenna elements, which can lead to increased signal gain and improved reception sensitivity, and smaller beam width. First, as the number of antenna elements increases, so does the cumulative signal power generated by the antenna elements. Second, in an ESA or AESA antenna system, for example, the increased number of steerable antenna elements can allow for distinguishing between a larger number of signals' phase shifts or time delays, and therefore better spatial discrimination between physical targets.
ESA or AESA antennas are typically built on monolithic printed circuit boards (PCBs). Manufacturing relatively large monolithic PCBs to accommodate large UWB (or U2WB) antenna arrays is technically challenging and has a poor yield. Wavelength scaled aperture (WSA) antenna arrays can allow for supporting UWBs or U2WBs with relatively smaller number of antenna elements compared to, for example, non-wavelength-scaled antenna arrays. However, even when using WSA configurations, antenna arrays are still desired to have a large number of antenna elements to achieve increased signal gain and improved reception sensitivity.